Manufacture of catalysts



' "{tented Mar. 30, 1948 Elmer B. Kanhoier, Riverside, 1",, assignor toUniversal Oil Products Company, Chicago, 111., a corporation of DelawareNo Drawing. Application July 30, 1945, Serial No. 607,904

1o Claims. (Cl. 252-250) This application is a continuation-in-part ofmy co-pending application Serial No. 485,151 (abandoned) filed April 30,1943, which in turn is a continuation-in-part of application Serial No.330.952 (abandoned) filed April 22, 1940.

This invention relates to a novel and improved method for themanufacture of silica and to the preparation of catalysts especiallysuitable for accelerating reactions among hydrocarbons. Morespecifically it has reference to a method of manufacturing finelydivided catalytic materials which are particularly effective inselectively promoting the formation of high antiknock motor fuel fromhigher boiling hydrocarbons or petroleum fractions having low antiknockvalue. The

preferred catalysts are particularly characterized by their finetexture. They consist of definite components and are preparedsynthetically by definite procedures which are specific in theproduction of catalysts of high activity and stability under relativelysevere conditions of service during processing and reactivation periods.

Manufacturing processes are generally known wherein hydrous oxide gelsare composited in the preparation of catalysts useful in varioushydrocarbon conversion processes. Hydrated silica' is one of the hydrousoxides which has been composited with various hydrous oxide gels such asalumina, for example, in the preparation of catalysts. The conventionalgels are prepared and composited by a number of different methods inwhich especial care is employed as to the manner in which the reagentsare mixed, the concentrations used, etc., so that the hydrated silicagel and/or the other hydrous gels composited either form a gel, or a solwhich sets on standing to form the gel. In contradistinction thereto, ithas been found that a particularly desirable type of highly active andstable catalysts can be produced according to the present invention bythe formation of Very finely divided precipitates thereby incidentallyavoiding, among other things, the major dimculties which usually attendwashing and filtration of undried gels.

In a broad aspect, the present invention relates to a process forproducing finely divided nongelatinous silica which comprisescommingling mineral acid with a solution containing not more than 30% byweight of an alkali metal silicate, about 7 to about 15% by weight of analkali metal halide, and about 51 to about 91% by weight of water.

In another aspect, the present invention comprises the manufacture ofcatalytic materials suitable for use in hydrocarbon conversionreaczirconia, or hydrated alumina and hydrated zirconia.

In a specific embodiment the present inven-- tion comprises a processfor the preparation of finely divided silica-alumina type composites byfirst precipitating finely divided hydrated silica by commingling amineral acid with a solution containing not more than 30% by weight ofan alkali metal silicate, about 7 to about 15% by weight of an alkalimetal halide, and about 51 to about 91% by weight of water, washing saidhydrated silica to the substantially complete removal of alkali metalcompounds, and compositing the washed silica with hydrated alumina.

In a further embodiment the alumina may be added to the silica bysuspending the latter in a solution of an aluminum salt andprecipitating hydrated aluminum oxide by the addition of a volatilebasic precipitant such as ammonium hydroxide.

According to the present invention, finely divided hydrous oxides ofsilicon are composited with other hydrous oxides to give highly'activeand stable catalysts particularly useful in hydrocarbon conversionreactions, said hydrous oxides of silicon being precipitated as veryfinely divided particles which tend to remain in suspension forprolonged periods of time as contrasted with gelatinous precipitates orsols which set into gels upon prolonged standing.

The precipitation of the hydrated silica is brought about underdefinitely controlled conditions in the presence of an added substance.such as a salt and particularly a halide of an alkali metal. The finelydivided precipitate may vary as to its degree of dispersion dependingupon the specific details of rocedure employed. but preclpitates highlysuitable for use as powdered catalysts have been prepared where theparticles are so small and of such a nature that they exhibit little orno tendency to settle out of suspension for prolonged periods of time.It has been found in some cases that the formation 01' finely dividedmaterial depends not only on the nature and amount of the alkali metalcompound added and the point at which it is added in the process butalso upon the dilution of the reactants and the manner in which thereactants are mixed as will be hereinafter illustrated.

The compounds which are used in accordance with the present invention toinsure the precipitation of hydrated silica in a fine state ofsubdivision are the halides oi' the alkali metals and particularly thechlorides thereof. The most generally utilizable compound is ordinarysodium chloride since this is cheap and readily available and gives goodresults. The amount oi added alkali metal halide which needs to bepresent either in the alkali metal silicate solution or in the acid withwhich the alkali metal solution is composited to cause the precipitationof silica in finely divided condition will varywith the salt itself,with the dilution of the solutions and with the method of compositing.

Various methods may be employed in preparing the finely divided silicafinally present after acidification to a pH value of about 2 isessentially hydrated silica holding a small amount of alkali metalcompounds by occlusion.

As an example of one method of compositing hydrous oxides, a finelydivided hydrated silica may be admixed while still in suspension with aseparately precipitated hydrated oxide. In another method the suspensionof hydrated silica may be mixed with a solution of a salt of the 'metalwhose hydrated oxide is to be precipitated finely divided hydratedsilica and compositing' with other hydrous oxides in accordance with thepresent invention depending upon the particular use to which thecomposite is to be put. A finely divided hydrated silicate may beprepared by adding an acid to an alkali metal silicate such as acommercial grade of water glass diluted with approximately'3 to timesits volume of water and containing an added amount of sodium chlcrideinsuring the formation oi finely divided hydrated silica. A minimumamount of sodium chloride is used for a particular dilution of waterglass and acid is gradually added while thoroughly agitating, in anamount sufilcient to precipitale a finely divided hydrated silica. Therate of addition of the acid should not be rapid, however, as too rapidacidification may tend to term gelatinous silica even when an alkalimetal halide is present. It is necessary even where the proper amount ofthe added substance is present to thoroughly mix the reacting solutionsand employ mixing times of 5 to minutes or more depending upon the sizeof batch and other factors- An extensive series of experiments showdefinitely that there were definite proportionsoi the three componentsof the mixture which must be employed ii the desired finely dividedhydrated silica was to be produced. The ranges in which these com onentsmay be present to form finely divid d silica and not a gelatinous massare (l) the alkali metal silicate should not be present in excess of byweight of the solution, (2) the alkali metal halide should be present ina range of about '7 to about 15% by weight of said solution, and (3)water in excess of that present in the alkali metal silicate should bebetween about 51 to about 91% by weight of the solution. Under theseconditions, commingling the solution with a mineral acid will result inthe production of finely divided non-gelatinous silica, wh reas if toosmall an amount of added alkali metal hal de is present the silica isproduced in a gelatinous form. Similarly, if too great an amount ofakali metal halide is present the process is inoperative because thesolubility of the sod um chloride is exceeded and silica precipitates whn the salt is added before the acidification of the solution. When thewater glass is present in an amount greater than 30% by weight or thesolution, the silica precipitated in a finely divided non-gelatinouscondition but the suspension was too viscous and it was diillcult torecover and wash the precipitated silica.

When acidifying a water glass containing sodium chloride, anintermediate precipitate is observed before sufiicient acid has beenadded to precipitate all of the silica. These intermediate pre ipitateshave been found to be insoluble and highly siliceous complexescontaining varying amounts of alkali metal compounds. As the remainingportions of the acid are added, the composition oi' these precipitateschanges so that in the'presenoe of the finely divided hydrated silieaand an alkaline precipitant may then be added to precipitate the hydrousoxide. In the case of a composite prepared in this manner, the hydrousoxide is precipitated in the presence of not only the added salt, butalso the salt formed by the neutralization of the alkali metal silicatewith the acid added to precipitate the hydrated silica. These salts orsalt solutions in this and subsequent procedures may be reused insubsequent preparation. Variations of this procedure may be employedwhereby the primary hydrated silica is filtered and separated from thesalt solution, washed and purified if desired and re-slurried orotherwise used for compositing with the remaining hydrous oxidecomponent. According to this last-named method, a finely dividedhydrated silica may be precipitated, filtered and washed to removealkali metal impurities by certain alternative methods which will besubsequently described, the purified hydrated silica then dispersed in asolution containing aluminum chloride, for example, and hydrated aluminaprecipitated in the presence of the finely divided hydrated silica bythe addition of ammonium hydroxide.

The finely divided hydrated silica is-preferably filtered and washed toremove substantially all alkali metal compounds and then intimatelycomposited with the other hydrous oxides such as those of alumina and/orzirconia, which may have been separately precipitated. Alternatively thehydrated silica is mixed with a solution of the salts of the metal ofthe hydrated oxide to be precipitated in and on its surfaces, and abasic reagent is then added to precipitate a hydrous oxide such asalumina and/or zirconia. The basic reagent employed may be an alkalimetal hydroxide, ammonium hydroxide or alkaline precipitants generally,and the amount added may be such that the pH is not far removed from theneutral point.

The hydrous oxides composited with the finely divided, hydrated silicamay be those of aluminum. zirconium, vanadium, thorium, chromium,molybdenum and numerous other metals yielding composites with hydratedsilica having catalytic properties. Various proportions of silica andsuch oxides may be composited, the more frequent practice being toemploy minor amounts of added hydrous oxides and major proportions ofhydrated silica. highly effective silica-alumina catalysts,approximately 5 to 30 percent of hydrated alumina is preferablycomposited with the silicon. Smaller and higher proportions of aluminamay also be utilized. Similarly, hydrated zirconia or other hydrousoxides may be employed or mixtures of these hydrous oxides, good resultshaving been obtained in cracking reactions using catalysts comprisingsilica, alumina and zirconia, composi'ted according to this invention.Highly active catalysts have been produced by compositing several molsof alumina and 5 t 10 mols of zir- Thus in the preparation or conia with100 mols oi the specially prepared silica.

Suspensions oi.the precipitated silica or its composites with otherhydrated oxides may be washed in any convenient form oi filtrationapparatus such as a filter press or centrifugal filter wherein the greatbulk oi the liquid is removed and a filter cake formed which may bewashed with comparative ease as contrasted with gelatinous precipitatesor gels. It has been found desirable when producing catalystcomposites'in a highly active and stable form to carefully wash theprecipitates and/or composites free from salts and particularly alkalimetal impurities. This may be accomplished by using various reagentssuch as, for example, washing with various acid and salt solutions.Water acidulated with strong acids may be used or solutions of salts orammonium, -or metals corresponding to those of the added metal oxidesfor example. The composite materials may be purified-before or afterdrying. These purification processes may be employed on the silica priorto its compositing with the remaining hydrous oxides. The compositedmaterials may be finally dried at temperatures of approximately ZOO-250F., more or less.

The catalysts produced by the present procedure are very finely dividedas compared with products from similar materials prepared from gels byformer methods as illustrated by the fact that aqueous suspensions ofthe material in preparation are very slow in settling out. Somepreparations having particular sizes of the order of to 20 microns, andif formed and shaped contact masses are prepared from them, the formedparticles are approximately one-half as dense as corresponding particlesproduced from gels. If desired the finely divided materials may beformed into shaped particles by the conventional consolidating andshaping processes such as pilling and briquetting, or they may beextruded. Various lubricants may be employedto facilitate pelleting suchas graphite, hydrogenated vegetable oil, certain metal palmitates andstearates, etc., and organic materials such as flour, starch, etc.

The finely divided catalyst composites are highly suitable forsuspending in a stream or oil which is processed under suitableconditions of temperature, pressure and contact time to carry outhydrocarbon conversion reactions to produce large yields of highantiknock gasoline. The kind of powdered catalyst used is not restrictedto any single preparative procedure since various types of oil crackingmay be carried out in the presence of the powdered catalyst. In thecracking of a heavy oil where in some cases it may not be desired torecover the catalyst, it may not be necessary to purify or even dry thepowdered product. 0n the other hand, in many operations. it will bedesirable to use a highly stable form of the catalyst which is separatedfrom residual and carbonaceous deposits and repeatedly regenerated.Large yields of gasolines having high octane numbers have been obtainedper pass as illustrated in the specific examples given hereinafter. Thepowdered catalyst may be separated from the oil by various proceduresand the separated catalyst regenerated by removing the hydrocarbonaceousdeposits by processes such as by solvent treatment or heating in thepresence 01' air whereupon it is used again either alone or in admixturewith fresh catalyst in suspension in the hydrocarbon oil processed.

The useiulness oi this material. however, is not restricted to its usein powdered iorm since it may be formed into particles anddisposed inbeds in catalyst reactors through which preheated vapors are passed atreaction temperatures. In this type oi operation. the catalyst isintermittently regenerated by heated oxidizing gas mixtures wherebycarbonaceous deposits are removed. I

The following specific examples are given to illustrate applications ofthe process of the invention, the activity of the catalyst preparationalso being indicated. However, the invention should not be considered aslimited to these examples or the process or to the particular catalystpreparations since these are merely given as illustrations.

- Y trample I A silica-alumina catalyst was prepared by diluting a.commercial sample of water glass approximately 5 times with water andmixing therewith approximately one-half oi the weight of water glass oisodium chloride dissolved in about the same amount or water used todilute the water glass. Diluted h drochloric acid was added to the waterglass-sodium chloride solution while agitating thoroughly and asuspension of very finely divided hydrated silica formed while thesolution was still alkaline. An excess or acid was then added and thiswas subsequently partly neutralized by the addition of ammoniumhydroxide. A solution of aluminum chloride in water was then added tothe hydrated silica suspension and after thorough mixing, ammoniumhydroxide was added to precipitate hydrated alumina in the presence orthe suspended silica, the ammonium hydroxide being added until theliquid was substantially neutral. The composite precipitate was thenfiltered, the filter cake dried to substantial dryness, and the driedmaterial washed with acidulated water until the washings weresubstantially free from sodium ions.

The catalyst produced in this manner, when admixed with a Pennsylvaniadistillate oil and heated to a temperature of approximately 750- 800 F.under a pressure of pounds per square inch gave a yield of approximately62% of 350 F. end point gasoline having approximately 78 octane number.

Example H A sample of powdered catalyst was prepared as follows: 90pounds of sodium chloride were dissolved in gallons of water and poundsor commercial water glass containing 8.9% NarO and 28.1% $102 was addedto the salt solution which was then further diluted to approximatelygallons. Concentrated hydrochloric acid was gradually added to thediluted-sodium silicatesodium chloride solution while agitating. Theaddition of acid was continued until the liquid still remained slightlyalkaline at which point a very finely divided silica suspension wasformed. An excess of acid was then added and the excess acidsubstantially neutralized with ammonium hydroxide. The silica suspensionwas then pumped into another tank containing approximately 20 gallons ofa solution containing 20 pounds oi-aluminum chloride. Ammonium hydroxidesolution was then added to precipitate hydrated alumina in the presence01' the finely divided hydrated silica in suspension, ammonium hydroxidebeing added until the solution was substantially neutral. The compositeprecipitate was then filtered on a centrifugal filter and washed bymeans or acidulated water to remove alkali metal impurities. The washedcake was dried at approximately 250' l". The dried material was afiufi'y powder oi very fine texture.

Catalyst prepared in this manner, admixed to the extent oi approximatelyV; of 1%by weight with a Pennsylvania gas oil oi approximately 36 A. P.I. gravity and heated to a reaction temperature of approximately 800'I". at a pressure or approximately 50 pounds per square inch, yielded ina single pass 28 volume percent of 400 1". end point gasoline having anoctane number 78. The catalyst is readily separated irom the oil and iscapable oi further use on regeneration either alone or in admixture withireshcatalyst.

trample III continued until the liquid still remains slightly alkalineat which point a very finely divided silica suspension is formed. Anexcess of acid is then added and the excess acid substantiallyneutralized with ammonium hydroxide. The silica suspension is thenfiltered, the filtrate being saved for re-use in subsequent batches, andis then carefully washed with water containing a small amount oraluminum chloride in solution until the washings are substantially freeirom alkali metal ions. The purified silica is suspended in water andpumped into a tank containing approximately gallons of aluminum chlorideand zirconyl chloride solution. Ammonium hydroxide solution is added toprecipitate hydrated alumina and hydrated zirconia in the presence ofthe silica suspension whereupon the composited precipitate is filteredand the filter cake dried to substantial dryness at approximately 250'I". Catalysts prepared in this manner will give substantially the sameresults as indicated above in -cracking operations and are readilyregenerated for repeated use in further cracking runs.

I claim as my invention:

1. A process for producing finely divided nongelatlnous silica whichcomprises commingling a mineral acid with a solution containing not morethan 30% by weight oi an alkali metal silicate, about 'lto about 15% byweight of an alkali metal halide, and about 51 to about 91% by weight ofwater.

2. A process for producing finely divided nongelatinous silica whichcomprises commingllng a mineral acid with a solution containing not morethan 30% by weight of an alkali metal silicate, about 7 to about 15% byweight oi. an alkali metal chloride, and about 51 to about 91% by weightof water.

3. A process for producing finely divided nongelatinous silica whichcomprises commingling a mineral acid with a solution containing not'more than 30% by weight or sodium silicate, about 7 to about 15% byweight or sodium chloridter and about 51 to about 91% by weight of 4. Aprocess for producing a finely divided catalyst which comprisescommingling a mineral acid with a solution containing not more than byweight or an alkali metal silicate,.about 7 to about 15% by weight oi.analkali metal halide and about 51 to about 91% by weight of water.compositing the silica thus formed with a metal oxide toiorm an activecomposite having catalytic properties.

5. A process for the manufacture or a catalyst which comprises slowlyadding with thorough agitation a mineral acid to a solution containingnot more than 80% by weight of an alkali metal silicate, about 7 toabout 15% by weight of an alkali metal halide and about 51 to about 91%by weight oi water to precipitate from said solution finely dividednon-gelatinous particles 01' hydrated silica. compositing the hydratedsilica thus formed with a salt oi a metal capable of being converted tothe oxide thereof and form a composite having catalytic properties. 1

8; The process as defined in claim 5 further characterized in that saidsalt comprises an aluminum salt.

'l. The process as defined in claim 5 further characterized in that saidsalt comprises a zirconium salt.

8. The process as defined in claim 5 further characterised in that saidsalt is an aluminum salt and further in that a salt of zirconium is alsoadded to said silica and aluminum salt.

9. A process i'or producing a catalyst comprising silica and aluminawhich comprises commingling a mineral acid with a solution containingnot more than 30% by weight of an alkali metal silicate, about 7 toabout 15% by weight of an alkali metal chloride and about 51 to about91% by weight of water to precipitate finely divided hydrated silica,treating said silica to remove alkali metal ions therefrom, forming acomposite of treated silica and hydrated alumina, and heating the saidlast-named composite to remove a substantial portion or water therefrom.

10. A process for producing a catalyst comprising silica and zirconiawhich comprises commingling a mineral acid with a solution containin notmore than 30% by weight of an alkali metal silicate, about "I to about15% by weight of an alkali metal chloride and about 51 to about 91% byweight of water to precipitate finely divided hydrated silica, treatingsaid silica to remove alkali metal ions therefrom, forming a compositeof treated silica and hydrated zirconia, and heat ing the saidlast-named composite to remove a substantial portion of water therefrom.

- mm B. KANHOFER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,012,911 Poulson Dec. 26, 19111,642,880 Kriegsheim et al. Sept. 29, 1921 2,229,353 Thomas et al. Jan.21, 1941 2,280,650 Kassel Apr. 21, 1942 FOREIGN PATENTS Number CountryDate 5,783 Great Britain June 8, 1914

